Electron Plus 1
                               ===============
+--------+-----------------------------+-------------------------------+
|        |           Write             |            Read               |
+========+=============================+===============================+
|  FC60  |                             |                               |
+--------+-----------------------------+-------------------------------+
|  FC61  | Clock Select Register A     | Status Register A             |
|        |  b7-4: Rx baud              |  b7: Break received           |
|        |  b3-0: Tx baud              |  b6: Receive Framing error    |
|        |   If ACR.b7=0:              |  b5: Receive Parity Error     |
|        |    50,110,134,200,300,600,  |  b4: Receive data overrun     |
|        |    1200,1050,2400,4800,     |  b3: Transmit Register Empty  |
|        |    7200,9600,38000,x,x,x    |  b2: Transmit Register Ready  |
|        |   If ACR.b7=1:              |  b1: Receive Register Full    |
|        |    75,110,134,150,300,600,  |  b0: Receive Register Ready   |
|        |    1200,2000,2400,4800,     |                               |
|        |    1800,9600,19200,x,x,x    |                               |
+--------+-----------------------------+-------------------------------+
|  FC62  | Command Register            |                               |
+--------+-----------------------------+-------------------------------+
|  FC63  | Transmit Data Register      | Receive Data Register         |
+--------+-----------------------------+-------------------------------+
|  FC64  | Aux. Control Register       |                               |
|        |   b7=baud rate select       |                               |
+--------+-----------------------------+-------------------------------+
|  FC65  | Interupt Mask Register      | Interupt Status Register      |
+--------+-----------------------------+-------------------------------+
|  FC6x  |                   other 2681 registers                      |
+--------+-----------------------------+-------------------------------+
|  FC6D  | Output Port Configuration   | Input Port Bits               |
|        |                             |   b2 = CTS                    |
+--------+-----------------------------+-------------------------------+
|  FC6E  | Set Output Port Bits        |                               |
|        |   b0 = clear RTS            |                               |
+--------+-----------------------------+-------------------------------+
|  FC6F  | Reset Output Port Bits      |                               |
|        |   b0 = set RTS              |                               |
+========+=============================+===============================+
|  FC70  | ADC0884 AtoD control        | ADC0884 AtoD convertor data   |
+--------+-----------------------------+-------------------------------+
|  FC71  | Centronics parallel data    |                               |
+--------+-----------------------------+-------------------------------+
|  FC72  |                             | Status                        |
|        |                             |   b7: printer Busy            |
|        |                             |   b6: ADC conversion ready    |
|        |                             |   b5: Fire Button 1           |
|        |                             |   b5: Fire Button 2           |
+--------+-----------------------------+-------------------------------+
|  FC73  | ROMSTROBE                   |                               |
+========+=============================+===============================+
|  FCD8  | Unlock AP7 bank 5/6         |                               |
|  FCD9  | Lock AP7 bank 5/6           |                               |
|  FCDA  | Unlock AP7 bank 13/15       |                               |
|  FCDB  | Lock AP7 bank 13/15         |                               |
|  FCDC  | Unlock ABR RAM bank 0/2     |                               |
|  FCDD  | Lock ABR RAM bank 0/2       |                               |
|  FCDE  | Unlock ABR RAM bank 1/3     |                               |
|  FCDF  | Lock ABR RAM bank 1/3       |                               |
+========+=============================+===============================+